The novel CTX-M-116 β-lactamase gene discovered in Proteus mirabilis is composed of parts of the CTX-M-22 and CTX-M-23 genes.

The novel beta-lactamase gene bla(CTX-M-116) was identified in a Proteus mirabilis nosocomial isolate recovered from the urine of a patient in Moscow in 2005. DNA sequence analysis showed bla(CTX-M-116) to be a hybrid gene consisting of 5' bla(CTX-M-23) (nucleotides 1 to 278) and 3' bla(CTX-M-22) (nucleotides 286 to 876) moieties separated by an intervening putative site of recombination (GTTAAAT). A retrospective analysis of available bla(CTX-M) genes in the GenBank database revealed 19 bla(CTX-M) genes that display the same hybrid structure.